Although hazard classification is performed at predefined distances, the maximum permissible exposure (MPE) for extended-source diode lasers decreases as the distance from the laser increases. The MPE depends on the apparent angular subtense of the source, which is simply the magnified image of the emitting diode. Small diameter beams require special consideration.

The ultrashort pulsed laser ablation of silicon wafers deposited with 1 μm thin film of SiC was performed in air medium using a 1 mJ, 120 fs, 800 nm Ti:sapphire laser, the objective being to determine the self-focusing capability of air to produce nanostructures. The effects of pulse energy, the number of pulses, pulse repetition rate and x–y translation speed on t...

Authors:John DowdenDepartment of Mathematics, University of Essex, Colchester, Essex CO4 3SQ, United Kingdom

There are several components to the motion of the liquid material in the weld pool in laser keyhole welding. Observations have shown not only that it moves in the plane perpendicular to the axis of the laser, but also that it moves parallel to the laser beam. It has been recognized for many years that the motion in the direction perpendicular to the surface of the work piece is important in connection with arc welding; it has, however, received less detailed study in connection with keyhole welding. The possible mechanisms are reviewed from a mathematical standpoint and Maran...

For economical reasons it is desirable to apply the highest possible speed during laser welding. Increasing the welding speed at a certain laser power might result in insufficient penetration of the weld. This work describes the design of a feedback controller, which is able to maintain full penetration in mild steel sheets. An optical detector, which is placed inside the Nd:Yttrium&ndash...

A KrF excimer laser beam is used to induce controllable and high-contrast colors on a stainless-steel surface under different processing conditions. The laser beam acts as a localized heating source that promotes the formation of semitransparent oxide films of varying thicknesses and morphologies on the sample surface. Ellipsometry and atomic force microscopy were employed to understand the laser-induce...

Laser gas nitriding (LGN) has been applied to fabricate a TiN coating on the surface of NiTi alloy for the purpose of improving the surface properties. The microstructure, surface characteristics, and corrosion properties of the laser gas nitrided layer on NiTi alloy surface were investigated. The nickel release rate of the LGN specimen in Hanks’ solution was also investigated. The results of x-ray diffraction, x-ray photoelec...

The spectral band between 400 and 700 nm is termed “visible” in laser safety standards, this is not the full extent of the visible spectrum. Light, or visible radiation, is that which is perceived by the human eye, and the spectral bandwidth for vision is really larger, extending into what some r...

Laser systems are high investment production machines that require a high level of availability in order to be amortized. Laser condition monitoring methods can be used to avoid breakdowns and maintain a consistent quality. In particular elements such as the cover slide, which protect the focusing optics from getting splashed through the welding process, need to be monitored. The effects of dirt on the cover slide are detrimental to the beam quality reaching the workpiece and can cause a spontaneous failure of the cover slide. By using a laser ba...